Coated electrical condenser



June 27, l1950 REYNQLDS 2,512,874

COATED ELECTRICAL CONDENSER Filed July 6, 1944 Patented June 27, 1950 uNlTEos'rA'rEs PATENT orifice COATED ELECTRICAL CoNnE'Nsnn Julian L. Reynolds, Richmond, Va. Application July s, 1944, serial No. 543,722

1 Claim. (Ci. 11s-41) This invention relates generally to electrical condensers of the type in which individual sheets or the convolutions of a coiled sheet in the form of a continuous roll of a metallic conducting material, usually aluminum, are separated from one another by the use of a. nonconducting or dielectric material. The dielectric insulator may be either (a) individual sheets or a long continuous coiled length of the dielectric material, usually paper, or (b) a dielectric coating applied to Yboth surfaces of the individual sheets or continuous length of aluminum foil. More particularly, the invention relates to the latter (b) type of dielectric coated condensers.

In constructing the iirst mentioned type of aluminum-paper dielectric condensers, the individual sheets or the continuous coiled length of the paper dielectric are wider than the individual sheets or continuous length of aluminum foil and extend beyond the edges thereof, so that the electricity accumulated in the condenser Will be prevented from jumping from the edge of one aluminum sheet or convolution to adjacent ones. sulating the exposed edges of the aluminum foil by extending the dielectric pellicle cannot be applied to the dielectric coated type of condenser which dispenses entirely with the need of a dielectric separate and apart from the aluminum foil. As a result, condensers of the coated type have proven unsatisfactory due to the tendency of the accumulated electricity to jump from the edge of one aluminum pellicle to the other and thus dissipate the current and lower the electrical capacity of the condenser.

One of the objects of this invention is to overcome this shortcoming in the dielectric coated type of condenser. This is achieved by a peculiar and novel arrangement of the individual sheets or continuous length of the metallic foil, after these have been coated to provide the required dielectric insulation, as will be fully described hereinafter.

Another object of this invention relates to the compositions used in forming the dielectric coating, and to improved processes for applying the coating and for improving the performance of the condenser.

For the attainment oi the foregoing and such other objects of invention as may herein appear or be pointed` out, I have shown a number of embodlmentsof my invention in the accompanying drawing, wherein- Figure l is a cross sectional view of one form of my invention in its simplest or unit form comprising a four-ply lamination.

Figure 2 is likewise a. cross sectional view oi another form of my invention as employed in built-up form in a condenser having greater electrical capacity.

Manifestly, this manner of in-` Figure 3 is also a cross sectional view ot another form of built-up condenser lamination.

Figure 4 is a perspective view, somewhat diagrammatically shown, of the application of the invention to the formation of a long continuous length of condenser lamination adapted to be subsequently coiled or cut in making the condenser.

As mentioned in the statement of invention above, a serious difliculty has been encountered,

in the coated type of condenser, in preventing the electricity accumulated in the condenser from bridging across the edges of adjacent sheets or convolutions. I have overcome this shortcoming in coated condensers in a manner which will be best described with the aid of Figure 1, which shows this aspect of my invention in its simplest form. 'Ihere are shown two condenser elements designated lil and 20, each condenser element being constituted of a foil or sheet of a metallic conducting material, II and 2|, respectively, covered on their both surfaces with a dielectric coating, designated l2 and i3 in the case of element i0, and 22 and 23 in the case of the other condenser element 20. Both condenser elements Il and 2li are U-shaped and interlocked or interleaved in the manner shown in Figure 1 with the pellicle portion of one element, e. g., pellicle portion 20a of element 2l, received between the spaced pellicle Portions ila and I lb of the other condenser element Il.

The web portion of one condenser element prevents the accumulated electricity from jumping across the distal edges of the spaced pellicle portions of the other condenser element. That is, the web portion 20w of condenser element 2l prevents the bridging of the accumulated electricity across the distal edges of the pellicle portions Illa and lilb of condenser element il. Web portion Iiiw of element il prevents the jumping oi accumulated electricity from the distal edge o! pellicle portion Zila of element 2l to the edges of adjacent condenser elements (not shown in Figure 1) where the four-ply lamination unit (pellicle portion HIa-ZUa-lOb-Zlb) are builtup to form increased condenser capacity.

The inventive thought described in its simplest terms in Figure 1 in connection with a fourply pellicle unit may be applied in various ways to form condensers ot increased capacity; one suitable arrangement is shown in Figure 2, another appears in Figure 3. Referring ilrst to Figure 2, it will be seen that the condenser elements are of S-shape, two such S-shaped elements being shown in full, viz., Il and 5l. The elements are interlocked or interleaved in the manner shown in Figure 2. Thus, the pellicle portion a of element 4l is received between the spaced pellicle portions IIb and llc of element Il (onlypartiallyshown). Ontheotherhamtpolthe accumulated electricity from jumping across the edges of the condenser elements in the manner described above in connection with Figure 1. Another form of built-up condenser elements employing the principle of my invention is shown in Figure 3. This form uses U-shaped elements,

three such U-shaped elements, 28, I8 and 29 being shown in `full in Figure 3 and two other elements, I'I and I 9, only partially.

My invention may be applied to the continuous roll type of coated condenser, in the manner l shownl in Figure 4. Two rolls I4 and 24 of the metallic conductor foil are provided, both surfaces of the foil being coated with the dielectric material. The width of the foils unwound from rolls I4 and 24 is suillcient to'permit each of the foils to be bent back on itself to form a U-shaped element, respectively |01 and 201, the two elements being Iinterleaved in the manner described above in connection with the simple unit, Figure 1, of four-ply laminations. As clearly shown in Figure 4, the two rolls I4 and 24 are displaced longitudinally from one another so that the unwound continuous webs I5 and 25 from the respective rolls will overlap a predetermined extent, designated a in Figure 4. Foil web I5, which is positioned higher in Figure 4, is turned down or bent 180 upon itself, starting at point A, to form the U-shaped condenser element |01 with the overlapped portion a of the other foil web received between its pellicle portions. Condenser element I01 thus forms an inverted U. The other foil web is then turned upwardly, at a point B beyond the said point of turning A of foil web I5, toA form the upright U-shaped element 201.'

In this manner a four-ply interlocked lamination may be made which may be used in its continuous length to form the convolution type of condenser, or which may be cut into short lengths for use in the type of condenser comprising a plurality of spaced sheets.

I have found the following substances suitable for the dielectric coating: cellulosic materials, such as nitro-cellulose, cellulose acetate, etc., which may be used alone or together with waxes, resins, etc.; phenol formaldehyde, the vinyls and poly vinyls, such as vinyl chloride, acetate, styrene, butyral, etc.; combinations of rubber, rubber chlorides, etc.

I have found that the addition of such materials as ethyl cellulose to my dielectric coating,

when this is compatible with the other ingredients. will lend durability and toughness to the coating and prevent scuiing or abrasion of the coating which would reduce its physical strength or destroy its dielectric properties.

Where the dielectric coating which I add to the surfaces of the condenser foil or the method by of treating a very thin foil, say of .00015"calipor, I rst apply a thin paper tissue to either one or vwhich it is necessary to apply it will not permit both surfaces of the foil. The dielectric coating material, such as those enumerated above, serves as an adhesive to bind the tissue to the condenser pellicle element. When greater dielectric strength is desired, I coat the combined lamination of tissue and condenser foil or sheet with another protective coating which may be either the dielectric resinous or rubber coating or may be a coating of pure wax or wax combination.

After my condensers are somade by the methods herein outlined, I may subject them to a bath or toa coating which tends to prevent moisture or harmful gases or other agents from attacking the condenser. I have found asphaltum best suited for providing a water-resisting covering. It is understood that condenser foil when subjected to various chemical or electrical treatments such as anodizing electrolysis are also included in the scope of nyrinvention. This may include the treatment of aluminum with sodium hydroxide or other alkaline earthy hydroxides, or it may also include acid etching treatments whereby the total exposed surface 0f a given square area of sheet is greatly increased du to the iinely pitted surface of the foil; In order to accomplish this, electrolysis may be used whereby portions of the surfaceof the metallic condensing foil are removed in suitable electrolyticl baths.

Having described my invention, what I claim and desire to secure'by Letters Patent, is as follows:

A. coated electrical condenser consisting of a plurality of foil sheets, of a metallic conducting material covered on both of its surfaces with a dielectric coating, each sheet being bent into U-shaped formation, and successive sheets being reversed in position and interleaved in such manner that each U-shaped dielectric sheet receives and encloses the legs of two associated sheets, the distal edges of the associated sheets thereby being shielded, and the structure reinforced by the interleaving, the interleaved legs of the various sheets being substantially equal in length.

JULIAN L. REYNOLDS.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 239,371 De Forest Mar. 29, 1881 1,324,792 Booth Dec. 16, 1919 1,609,320 Smith Dec. 7, 1926 1,726,343 Danziger Aug. 27, 1929 1,886,997 Wilkins Nov. 8, 1932 1,904,825 Friberg Apr. 18, 1933 1,947,112 Ruben' Feb. 13, 1934 2,203,283 Miller June 4, 1940 2,223,173 Haase Nov. 26, 1940 2,244,090 Traub June 3, 1941 2,300,072 Smyers Oct. 27, 1942 2,394,670 Detrick Feb. 12, 1946 FOREIGN PATENTS Number Country Date 437,429 Great Britain Oct. 29, 1935 

